The present invention relates to a passenger conveyor system, and more particularly to a mechanism for a moving skirt in chain driven escalators and moving walks.
A typical passenger conveyor, such as an escalator or moving walk, includes a series of tread plates, a frame, a drive, a step chain and a pair of balustrade assemblies. The frame comprises a truss section on both the left and right hand sides of the frame. Each truss section has two end sections forming landings, connected by an inclined midsection. Matching pairs of roller tracks are attached on the inside of each truss section, i.e. the side of the truss section facing the other truss section. The upper landing usually houses the escalator drive between the trusses. The drive powers a pair of step chain sprockets, which in turn impart motion to the step chain to move the tread plates. The step chain and tread plates travel a closed loop, running from one elevation to the other elevation, and back.
Step chains typically include a pair of chain strands connected by a plurality of axles, each axle having a pair of rollers that contact the roller tracks. The tread plates are connected to the axles. The chain strands are attached to the axle inside of the rollers. Each strand is formed from a plurality of chain links. Because there are commonly a number of chain links between axles and thereby between successive tread plates in a chain driven escalator, the spacing between adjacent tread plates may vary in transition regions of the closed loop path as the multiple chain links follow the non-linear shape of the transition regions.
The individual steps of an escalator typically move in a very narrow “channel” defined by panel elements that are commonly referred to as the skirt boards. These skirt boards are attached to the frame of the escalator, and therefore remain fixed as the steps move therebetween. The gap between the steps and the skirt board is kept very small to decrease the likelihood that objects or body parts of passengers are pulled into and trapped in this gap. Designing escalators with a very small gap between steps and skirt boards significantly increases installation and maintenance costs and complexity. Some escalators therefore employ a moving skirt, also known as a guarded step, by providing a skirt board that moves with the steps. Moving skirts substantially remove the risk of trapping objects and passenger body parts in the gap between the step and skirt boards, because there is no relative motion between the two components.
One design challenge in chain driven escalators that employ a moving skirt is designing the skirt boards such that they accommodate the articulated motion of the steps throughout the closed loop path through which they travel during operation. In particular, the skirt boards must be designed to comply with variations in adjacent step spacing in transition regions of the closed loop path, such as in the turnarounds in the upper and lower landings of the escalator.